Brain injury is a common problem in accidents involving trauma to a person’s head, and as the brain controls the whole body, this can cause catastrophic effects on bodily function and condition. Science is still in the dark when it comes to preventing this damage, but it does have a few leads. One such lead, is that of the involvement of the NMDA receptor.
The NMDA receptor is one of the main receptors in the brain that lead to excitation of neurons. When glutamate and glycine in the body bind to this receptor, glutamate is released into neurons, which excites and opens them to an influx of ions. In this way, it is involved in many of the critical functions of neurons, such as learning and memory.
The role of NMDA receptors in brain injury
Whilst the immediate trauma suffered from a brain injury causes damage, a lot of the damage of a brain injury occurs in the hours and days after the original event. This process is called the ischemic cascade, and involves a lack of sufficient blood flow causing a cascade of effects where the brain is unable to get enough oxygen and the ion transport pumps fail, allowing too much calcium to enter the cells.
When calcium builds up in cells, it stimulates glutamate to be released, which in turn will stimulate the NMDA receptors to allow even more calcium into the cells. This causes a buildup of free radicals and enzymes to occur. Enzymes called phospolipases begin to break down the cell and eventually the cell is destroyed through apoptosis and all the toxins and enzymes leech out and are able to damage more cells.
Using NMDA antagonists to prevent brain damage
As it is the initial excitation caused by glutamate and the NMDA receptors that provokes the ischemic cascade to continue, much research is being placed on the role of NMDA antagonists in treating brain injuries, along with the regular treatment to increase blood flow. Trials of NMDA antagonist therapy have shown up to a 68 per cent reduction in ischemic damage following head trauma in cats.
Although NMDA antagonists may have a beneficial effect on preventing brain damage, glutamate is also necessary for cell survival and thus the use of NMDA antagonists may not have an appreciable effect if therapy is continued for too long. With no clear-cut methods to determine how long to appropriately use antagonists, there is more research needed before they can be used in the treatment of brain injuries.